To answer your question, Anon 1, ascots migrated to the luxury yaht scene. They're still fairly common among a certain class of "captain". These gentlemen still value how effectivley a snappy ascot conceals their wattled, saggy negks and snow-white chest hair.

As for the mainstream, the look was (at its best) just a little too "dude western" and ended up looking like this.https://i.pinimg.com/736x/0f/60/bc/0f60bcfb72ab4b83a57d5afb45aa123f--mens-vintage-vintage-fashion.jpg

At their least flattering, ascots looked effeminate on a lot of men. When Elton John started wearing them on stage, that was it.

The only guy who ever looked completely put-together wearing an ascot was Fred on Scooby Doo.